PowerColor RED DRAGON Radeon RX 580 DirectX 12 AXRX 580 8GBD5-3DHDV2/OC 8GB 256-Bit GDDR5 PCI Express 3.0 CrossFireX Support ATX Video Card
Get 2 free games w/ purchase, limited offer
-- $170 at Newegg USA today.
Your friend's CPU is not at all bad for gaming -- assuming a good motherboard and up to date OS and drivers, etc. 4 cores are still enough.
Our AMD RX580 (cost $165 on sale) runs on a much more out of date AMD CPU (that's slower than your friend's CPU) and runs everything I play at 1080p and ultra settings at smooth frame rates. Also runs things I play at 1440p and ultra -- with occasional drops below 30FPS on heavily modded games. I have it on a 4K monitor that we use at 2K (1440p) -- 4K works but the print is too small to read (in any case, I don't recommend RX580 for 4K gaming). It is not our main PC. Obviously, there are faster FPS cards -- for more money.
Of course, Nvidia's GTX1060 6GB (3GB not recommended) can be had for $200 with some free games at the same Newegg site.
Just an opinion from a distance by an AMD fan.